Hearing assistance devices, such as hearing aids, are used to assist patients suffering hearing loss by transmitting amplified sounds to ear canals. In one example, a hearing aid is worn in and/or around a patient's ear.
Frequency lowering algorithms in hearing aids reproduce high-frequency speech cues (such as fricative consonants) at lower frequencies for hearing aid wearers having severe high frequency hearing loss. These frequency lowering algorithms perform poorly in noise, where they are most needed, because consonant detection and extraction is difficult in the presence of noise. Noise tends to obscure the spectral cues that define and differentiate consonants because consonants themselves tend to be noise-like, and because they often tend to have less energy than voiced parts of speech (vowels), especially when they appear at the end of a word. For signal-driven algorithms, the frequency transposition activity may be driven more by noise than speech, because the signal is dominated by the noise, and the translated spectral features are therefore those of the noise. Such algorithms may not provide useful consonant cues in such situations, and when they do, the cues may be poorly differentiated (that is, all consonants sound the same), because spectral contrasts that would ideally be preserved by the algorithm are absent in the noisy speech signal.
There is a need in the art for improved frequency translation in hearing assistance devices.